Ashlu Creek Impact Study - BC Hydro - Transmission

Ashlu IPP Impact Study June 2006 

Impact Study 

For the Ashlu Creek Power Development Project 

Of 

XXXX 

Report No. SPA 2006-093 

June 2006 

Regional System Planning 

British Columbia Transmission Corporation 

© British Columbia Transmission Corporation, 2006. All rights reserved. 

i


DISCLAIMER OF WARRANTY, LIMITATION OF LIABILITY 

This report was prepared by BCTC solely for the purposes described in this report, and is 

based on information available to BCTC as of the date of this report. Accordingly, this 

report is suitable only for such purposes, and is subject to any changes arising after the 

date of this report. 

Unless otherwise expressly agreed by BCTC, BCTC does not represent or warrant the 

accuracy, completeness or usefulness of this report, or any information contained in this 

report, for use or consideration by any third party, nor does BCTC accept any liability out 

of reliance by a third party on this report, or any information contained in this report, or 

for any errors or omissions in this report. Any use or reliance by third parties is at their 

own risk. 

________________________________________________________________________________________________________________________________________________ 

This document contains proprietary information and shall not be reproduced in whole or in part without the prior written consent of BCTC 

ii


Executive Summary 

This report assesses the impact of the interconnection of the proposed 61 MVA 

generation and its facilities tapped at BCTC’s Cheakamus- Cheekeye (CMS-CKY) 230 

kV line 2L12 at 2 km from the CMS end. The report also provides a review and identifies 

requirements to connect the proposed generation to the Transmission System. 

In order to connect the proposed generation and its facilities to the Transmission System, 

the following conclusions are identified in this impact study: 

• The IPP and its facilities will be tapped to the 2L12 of BCTC as the Point of 

Interconnection (POI) to the Transmission System. 

• No unacceptable abnormal voltage instability due to Ashlu IPP connection has been 

observed in the Transmission System. 

• Transmission equipment overload has been observed during heavy summer system 

operating conditions. 2L12 has to be upgraded to higher operating temperature from 

50 to 63 degree C or higher. 

The Interconnection Facilities Study report will provide more details with cost estimates 

of the system upgrade requirement for connecting this IPP. 

________________________________________________________________________________________________________________________________________________ 


iii


Executive Summary 

Table of Content 

1.0 Background 1 

2.0 Purpose of Study 1 

3.0 Study Assumptions 1 

4.0 System Studies 1 

4.1 Steady State Power Flow study 1 

4.2 Short Circuit study 2 

4.3 Power Flow Based First Contingency study 2 

4.4 Reliability study 3 

4.5 Transient Stability study 3 

4.6 Islanding 4 

4.7 Black Start Capability 4 

5.0 Conclusion and Discussions 4 

Appendix 

Load flow one-line Diagram for normal and contingency conditions 6 

Models for IPP power plant excitation control system 10 

Stability swing of rotor angle for 3 phase fault on CKY 230 kV bus 14 

Stability swing of bus voltage for 3 phase fault on CKY 230 kV bus 15 

Stability swing of line flow for 3 phase fault on CKY 230 kV bus 16 

Stability swing of bus frequency for 3 phase fault on CKY 230 kV bus 17 

________________________________________________________________________________________________________________________________________________ 


iv


1.0 Background 

XXXX plans to develop the 61 MVA Ashlu IPP Project consisting of 3 generator units in the 

Ashlu power plant site. The maximum power to be injected into the Transmission System is 

55 MW. The proposed in-service date of this IPP is April 2008. 

The proposed Point of Connection (POI) of the IPP and its facilities is 2 km from the CMS end 

of the BCTC 230 kV line 2L12 (CMS-CKY) . Power generated by the IPP will be transferred 

by the 2L12 line via CKY to the Transmission System. 

2.0 Purpose of Study 

This study assesses the requirements for interconnecting the IPP and its facilities into the 

Transmission System based on the impact to the regional transmission network. This impact 

study identifies system constraints and network upgrades required for the reliable operation of 

the inter-connected IPP and the Transmission System. 

3.0 Study Assumptions 

The study is carried out based on the model, data and information provided by the IPP for the 

inter-connections application process. The 2009 winter peak and 2009 summer peak and light 

load base cases are used. 

4.0 System Studies 

Power flow, short circuit, voltage stability and transient stability studies were carried out to 

evaluate the feasibility of the proposed interconnection and to identify the IPP connection 

requirements. 

4.1 Steady State Pre-outage Power Flows 

Pre-outage power flows are prepared to assess the impact of the IPP connection. The 

study includes three basic load / generation conditions: the 2009 winter peak, 2009 

summer peak and 2009 summer light load conditions. IPP maximum output is assumed 

in all case studies. 

Results indicate that, under system normal conditions, the thermal loadings of 2L12 

will be exceeded in the heavy summer operating conditions. The detailed normal 

system conditions are shown in Figures 1 to 3. 

Regional System Planning 1

4.2 Short Circuit Study 

Increase in fault levels at remote stations due to Ashlu IPP remains within the existing 

equipment ratings. 

Fault Levels expressed as Thevenin Impedances at point-of-interconnection on 2L12 

are: 

Present Fault Level (including Ashlu IPP): 

Z + = R + + jX + = 2.0 + j18.1 ohms 

Z - = R - + jX - = 2.1 + j18.5 ohms 

Z 0 = R 0 + jX 0 = 1.3 + j20.0 ohms 

Present Fault Level (excluding Ashlu IPP): 

Z + = R + + jX + = 2.34 + j19.5 ohms 

Z - = R - + jX - = 2.34 + j19.5 ohms 

Z 0 = R 0 + jX 0 = 1.7 + j24.1 ohms 

Ultimate Fault Level: 

3-phase fault = 5000 MVA 

X/R = 10 

(assumed) 

SLG fault: 12.5 kA rms sym. 

The foregoing assumes 1.05 x the base voltage of 230 kV. This is the minimum level 

recommended for 230 kV stations for the BCTC system and provides adequate 

capability for an ultimate 500 – 230 kV tie at Cheekye. 

The ultimate duty shall be used for the basic station design such as bus strength and 

ground grid and for any major equipment that the owner does not want to replace when 

the present fault level increases to the ultimate. No planned date exists for this 

increase. 

Ashlu Generator Step-up Transformer 

It is required that this be configured as a conventional generator transformer with a LV 

delta to HV grounded wye configuration. 

The recommended HV nominal tap for this transformer is 236 kV with +/-2 x 2.5% offload 

taps 

________________________________________________________________________________________________________________________________________________ 


2

4.3 Power Flow Based First Contingency Study 

Power flow based single contingency studies do not have any further transmission line 

loading problem. There is no voltage violation due to the addition of the Ashlu IPP. 

There is also no voltage stability issue upon loss of the largest load in this area, or loss 

of the Ashlu IPP. Summary of load flow study results are shown in Table 1. 

Table 1 Steady State Power Flow Study Results for Ashlu IPP Project 

System 

Load 

Condition 

2009 HW 

2009 HS 

2009 LS 

2009 HW 

System 

configuration 

Heavy 

winter- 

Normal 

Heavy 

summer- 

Normal 

Light 

summer- 

Normal 

Heavy 

winter- 2L13 

outage 

MW 

Injection 

from 

IPP 

CMS 

230 

Bus Voltage (in per unit) 

CKY 

230 

SQH 

60 

MAM 

60 

Power Flow (MW) 

2L13 

(CKY- 

CYP) 

2L12 

(CMS- 

CKY) 

2L9 

(CKY- 

LYN) 

Comment 

55 1.010 0.999 1.067 1.069 203 221 230 Fig. 1 

55 1.010 1.013 1.071 1.069 209* 134 132 Fig. 2 

55 1.048 1.048 1.085 1.080 54 82 84 Fig. 3 

55 1.010 1.000 1.068 1.069 203 outage 363 Fig. 4 

* 2L12 is overloaded to 106% summer rating. Present line conductor operating temperature 

is at 50 deg C. The addition of the Ashlu IPP will require that 2L12 be upgraded for a 

higher operating temperature. 

4.4 Reliability Study 

There is an existing BC Hydro 173 MVA CMS generating station connected on 2L12 

which the Ashlu IPP will be tapped on. A reliability assessment of the connection 

schemes of employing a disconnect switch (DS) versus a 3 breaker ring (3CB) at the 

POI has been performed based on line outage data. 

The unavailability of 2L12 for a 3CB scheme is 1.0 hours/year compared to 1.21 

hours/year for a DS scheme. Thus, for a small improvement in reliability (0.21 

hours/year) the 3-breaker ring configuration is not required from the system reliability 

point of view. However, the 2.5 km tap line from the POI to the IPP shall be designed 

and maintained to the 2L12 level. Otherwise, reliability of the CMS power plant will be 

reduced to an unacceptable level. 

________________________________________________________________________________________________________________________________________________ 


3

4.5 Transient Stability Study 

For transient stability studies, the IPP power plant is modelled in details as shown in 

Figures 5-1 to 5-3. Various system operating conditions including the most severe 

system operating conditions have been analysed. Detailed control block diagram of the 

excitation control system has not yet been available. Typical dynamics model for the 

proposed Basler DECS exciter series has been implemented. 

Transient stability performance has been identified to be acceptable for the various 

system contingencies with normal fault clearing times of 12 and 6 cycles for the 60 and 

230 kV network. The existing 2L12 protection is electromechanical and 

communication independent. It would need to be replaced since this existing slow 

protection is not acceptable. High speed permissive protection scheme will be required. 

However, out-of-step protection is required for the IPP as standard generator protective 

equipment against unexpected contingencies in the inter-connected IPP and 

Transmission System. Over-frequency relay for IPP generator protection during 

islanding conditions shall also be installed. Summary of system stability study results is 

shown in Table 2. 

Table 2: Transient stability study results ( 2009 heavy winter case) 

Case Outage 3Φ fault Clearing 

time 

(cycles) 

1* 2L13 

CKY-CYP 

2 CMS 13.8/ 

230 kV T2 

3 CKY 60/ 

230 kV T5 

IPP 

max 

rotor 

swing 

CKY230 6 42 

deg. 

CMS230 6 45 

deg. 

CKY 66 10 10 

deg. 

Minimum dynamic voltage level/ 

Comments for overall system swing 

conditions 

1.0 pu @ CKY 230 kV bus. / 

Acceptable system swings. 

0.99 pu @ CKY 230 kV bus. / 


1.01 pu @ CKY 230 kV bus. / 


* Results for Case 1 are shown in Figures 6-1 to 6-4 as typical system swing. 

System stability response of delayed clearing of single phase to ground fault is 

acceptable. However, delayed clearing of the more severe double phase to ground fault 

and three phase fault will cause unacceptable system stability conditions including 

voltages, power and frequency oscillations in the area. With the installation of the 

grounded Y IPP generator transformer, delayed fault clearing feature in 2L12 for overvoltage 

control is no longer required. 

________________________________________________________________________________________________________________________________________________ 


4

4.6 Islanding 

IPP will be required to provide over-frequency protection, which will initiate tripping of IPP 

entrance breaker should IPP islands connected to 2L12 but line terminal open at CKY and 

CMS. 

4.7 Black Start Capability 

Estimate voltage sag due to transformer energization is about 6%. Black start 

capability is not be required from the BCTC point-of-view. 

5.0 Conclusion and Discussion 

In order to interconnect the Ashlu IPP generation of 55 MW and its facilities into the 

Transmission System at BCTC’s 2L12 near the CMS Substation, this impact study has 

identified the following issues and requirements: 

• Transmission equipment overload has been observed during heavy summer system 

operating conditions. 2L12 has to be upgraded to higher operating temperature from 50 

to 63 degree C or higher. 

• No equipment overload or voltage violation has been observed under the normal and 

contingency conditions after 2L12 is upgraded. 

• No adverse transient stability impact on the Transmission System has been observed for 

the normal types of system disturbances. 

• The Basler DECS exciter proposed by the IPP is acceptable for reliable operation of the 

inter-connected BC Hydro and IPP power systems. 

• There will be no voltage stability concern for this IPP interconnection. 

• Three breaker ring configuration at the POI for connecting the Ashlu IPP is not 

required. In this particular instance, a tap line with disconnect switch connection 

scheme is permissible from the system reliability point of view. 

This impact study of the feasibility and requirements for Ashlu IPP connection is based on the 

best available data. Detailed system study with actual data can be performed as required in the 

later stage. 

Further information on system upgrade requirement and cost estimates will be provided in the 

Facilities Study report. 

________________________________________________________________________________________________________________________________________________ 


5

Appendix :-Figs 1 to 4 Power Flow Diagram of BCTC/ BCH system. 

Fig. 1 2009 Heavy winter case. 



Fig. 2 2009 Heavy summer case --- 2L12 (CMS- CKY) overloaded to 106%. 

________________________________________________________________________________________________________________________________________________ 


7


Fig. 3 2009 Light summer case. 

________________________________________________________________________________________________________________________________________________ 


8


Fig. 4 2009 Heavy winter case with 2L13 out of service. 

________________________________________________________________________________________________________________________________________________ 


9

GENSAL 

Salient Pole Generator Model 

This model is located at system bus #__ASU IPP_ IBUS. 

Machine #___80005___ I. 

This model uses CONs starting with #___________ J. 

and STATEs starting with # ___________ K. 

The machine MVA base is ____18.5_______for each of ____3___ units = 

___18.5___MBASE. 

ZSORCE for this machine is ____0.0______ + j ___0.12___ on the above MBASE. 

CONs # Value Description STATEs # Description 

J 5.5 T’ do (>0) (Seconds) K E’ q 

J + 1 0.03 T’’ do (>0) (Seconds) K + 1 ψkd 

J + 2 0.17 T’’ qo (>0) (Seconds) K + 2 ψ’’ q 

J + 3 1.67 Inertia H K + 3 Δ Speed ( p.u. ) 

J + 4 1.0 Speed Damping D K + 4 Angle ( radians ) 

J + 5 1.24 X d 

J + 6 0.67 X q 

J + 7 0.2 X’ d 

J + 8 0.12 X’’ d = X’’ q 

J + 9 0.08 X ι 

J + 10 0.154 S(1.0) 

J + 11 0.447 S(1.2) 

X d , X q , X’ d , X’’ d , X’’ q , X ι , H and D are in p.u., machine MVA base. 

X’’ q must be equal to X’’ d 

IBUS, ‘GENSAL’, I, T’ do , T’’ do , T’’ qo , H, D, X d , X q , X’ d , X’’ d , X ι , S(1.0), S(1.2)/ 

Fig. 5-1 Ashlu IPP power plant excitation control system model. 


ESAC8B 

Basler DECS 

This model is located at system bus machine# Ashlu-IPP G1/ G2/ G3 IBUS 

CONs # Value Description 

J 0.0 TR (sec) 

J+1 170. KP 

J+2 130. KI 

J+3 60. KD 

J+4 0.03 TD (sec) 

J+5 1.0 KA 

J+6 0.0 TA 

J+7 10.0 V RMAX or zero 

J+8 0.0 

V RMIN 

J+9 1.0 TE > 0 (sec) 

J+10 1.0 KE or zero 

J+11 3.38 E1 

J+12 1.36 SE(E1) 

J+13 4.5 E2 

J+14 1.5 SE(E2) 

STATEs # Description 

K Sensed VT 

K+1 Integral controller 

K+2 Derivative controller 

K+3 Voltage regulator 

K+4 Exciter output, EFD 

IBUS, ’ESAC8B’, I, TR, KP, KI, KD, TD, KA, TA, V RMAX, V RMIN, TE, KE, E1, SE(E1), E2, SE(E2)/ 

Fig. 5-2 Ashlu IPP power plant excitation control system model (cont’d) 

________________________________________________________________________________________________________________________________________________ 


11

PSS/E-29 

PSS2A 

IEEE Dual Input Stabilizer Model 

This model is located at system bus #__Ashlu_IPP_ IBUS. 

Machine #___80005____ I. 

This model uses CONs starting with #___________ J. 

and STATEs starting with # ___________ K. 

and VARs starting with # ___________ L. 

and ICONs starting with 

# ___________ IC. 

ICONs # Value Description 

IC 2 IC1, First Stabilizer Input Code: 

1 p.u. Rotor Speed Deviation 

2 p.u. Bus Frequency Deviation 

3 p.u. Generator Electrical Power on MBASE base 

4 p.u. Generator Accelerating Power 

5 p.u. Bus Voltage 

6. Derivative Of p.u. Bus Voltage 

IC + 1 0 REMBUS1, First Remote Bus Number 

IC + 2 3 IC1, First Stabilizer Input Code: 

1 p.u. Rotor Speed Deviation 

2 p.u. Bus Frequency Deviation 

3 p.u. Generator Electrical Power on MBASE base 

4 p.u. Generator Accelerating Power 

5 p.u. Bus Voltage 

6. Derivative Of p.u. Bus Voltage 

IC + 3 0 REMBUS2, Second Remote Bus Number 

IC + 4 5 M, Ramp Tracking Filter 

IC + 5 1 N, Ramp Tracking Filter 

CONs # Value Description 

J 10. T W1 (>0) 

J + 1 10. T W2 

J + 2 0. T 6 

J + 3 10. T W3 (>0) 

J + 4 0. T W4 

________________________________________________________________________________________________________________________________________________ 


12

J + 5 10. T 7 

J + 6 2.99 K S2 = T7/2H 

J + 7 1. K S3 

J + 8 0.5 T 8 

J + 9 0.1 T 9 (>0) 

J + 10 20.0 K S1 

J + 11 0.15 T 1 

J + 12 0.025 T 2 

J + 13 0.15 T 3 

J + 14 0.025 T 4 

J + 15 0.1 V STMAX 

J + 16 -0.1 V STMIN 

Fig. 5-3 Ashlu IPP power plant excitation control system model (cont’d). 

________________________________________________________________________________________________________________________________________________ 


13

Fig. 6-1 Stability swing of rotor angle for 3 phase fault on CKY 230 kV bus 


Fig. 6-2 Stability swing of bus voltage for 3 phase fault on CKY 230 kV bus 

________________________________________________________________________________________________________________________________________________ 


15

Fig. 6-3 Stability swing of line flow for 3 phase fault on CKY 230 kV bus 

________________________________________________________________________________________________________________________________________________ 


16

Fig. 6-4 Stability swing of bus frequency for 3 phase fault on CKY 230 kV bus 

________________________________________________________________________________________________________________________________________________ 


17

Ashlu Creek Impact Study - BC Hydro - Transmission

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?